In laboratory experiments with nonhumans, enhanced sensitivity to the effects of exogenous opiates has been demonstrated following cessation of chronic opiate antagonist administration. In this study we examined if chronic buprenorphine administration would generate supersensitivity to opiates. Opioid-dependent outpatients (n=3) were administered buprenorphine chronically. The dose of buprenorphine was varied systematically across conditions using an ABA reversal design. Subjects received initially a low dose of buprenorphine (2.0 mg) for 14 days and were then transitioned to a high dose of buprenorphine (16 mg) for 32 days prior to returning to the low dose condition for an additional 5 days. Sensitivity to exogenous opiates was assessed via hydromorphone challenge sessions conducted toward the conclusion of each condition. During these sessions, subjects were administered hydromorphone in cumulative s.c. doses of 0, 6, and 18 mg and physiological measures and ratings of agonist effects were collected repeatedly. The data from the session conducted during the initial low dose condition served as baseline measures from which to assess the effects of chronic administration of high doses of buprenorphine. Supersensitivity would have been evidenced by a pronounced leftward shift of the dose response functions relative to baseline measures upon return to the low dose condition. Shifts in the dose effect curves were assessed via comparison with data obtained from a control subject that was administered the low dose (2 mg) of buprenorphine throughout treatment. Based upon preliminary data, we found no evidence of buprenorphine induced supersensitivity. As a result, we have closed the study and will no longer be needing GCRC resources for this study.